In vivo detection of activated platelets allows characterizing rupture of atherosclerotic plaques with molecular magnetic resonance imaging in mice

BACKGROUND: Early and non-invasive detection of platelets on micro atherothrombosis provides a means to identify unstable plaque and thereby allowing prophylactic treatment towards prevention of stroke or myocardial infarction. Molecular magnetic resonance imaging (mMRI) of activated platelets as early markers of plaque rupture using targeted contrast agents is a promising strategy. In this study, we aim to specifically image activated platelets in murine atherothrombosis by in vivo mMRI, using a dedicated animal model of plaque rupture. METHODS: An antibody targeting ligand-induced binding sites (LIBS) on the glycoprotein IIb/IIIa-receptor of activated platelets was conjugated to microparticles of iron oxide (MPIO) to form the LIBS-MPIO contrast agent causing a signal-extinction in T2*-weighted MRI. ApoE(-/-) mice (60 weeks-old) were fed a high fat diet for 5 weeks. Using a small needle, the surface of their carotid plaques was scratched under blood flow to induce atherothrombosis. In vivo 9.4 Tesla MRI was performed before and repetitively after intravenous injection of either LIBS-MPIO versus non-targeted-MPIO. RESULTS: LIBS-MPIO injected animals showed a significant signal extinction (p/= 2% of the vascular lumen. Histology further confirmed significant binding of LIBS-MPIO compared to control-MPIO on the thrombus developing on the surface of ruptured plaques (p<0.01). CONCLUSION: in vivo mMRI detected activated platelets on mechanically ruptured atherosclerotic plaques in ApoE(-/-) mice with a high sensititvity. This imaging technology represents a unique opportunity for noninvasive detection of atherothrombosis and the identification of unstable atherosclerotic plaques with the ultimate promise to prevent strokes and myocardial infarctions

Characterizing Prostate Cancer Risk Through Multi-Ancestry Genome-Wide Discovery of 187 Novel Risk Variants

The transferability and clinical value of genetic risk scores (GRSs) across populations remain limited due to an imbalance in genetic studies across ancestrally diverse populations. Here we conducted a multi-ancestry genome-wide association study of 156,319 prostate cancer cases and 788,443 controls of European, African, Asian and Hispanic men, reflecting a 57% increase in the number of non-European cases over previous prostate cancer genome-wide association studies. We identified 187 novel risk variants for prostate cancer, increasing the total number of risk variants to 451. An externally replicated multi-ancestry GRS was associated with risk that ranged from 1.8 (per standard deviation) in African ancestry men to 2.2 in European ancestry men. The GRS was associated with a greater risk of aggressive versus non-aggressive disease in men of African ancestry (P = 0.03). Our study presents novel prostate cancer susceptibility loci and a GRS with effective risk stratification across ancestry groups

Vascular wall–produced prostaglandin E2 exacerbates arterial thrombosis and atherothrombosis through platelet EP3 receptors

Prostanoids, bioactive lipids derived from arachidonic acid (AA), are important for vascular homeostasis. Among them, prostaglandin E2 (PGE2) enhances aggregation of platelets submaximally stimulated in vitro. This results from activation of EP3, one of the four PGE2 receptors, which decreases the threshold at which agonists activate platelets to aggregate. Although PGE2 altered venous thrombosis induced by administration of AA, its role in pathophysiopathological conditions has remained speculative. We report that arterial walls subjected to inflammatory stimuli produce PGE2. In several models, we show that PGE2 produced by the arterial wall facilitates arterial thrombosis. Next, we detected PGE2 in mouse atherosclerotic plaques. We demonstrate that this plaque-produced PGE2 is not altered and is still able to activate EP3. In addition, we present evidence that PGE2 can leave the plaque and activate EP3 on blood platelets. Consistent with these findings, we observed that atherothrombosis induced in vivo by mechanical rupture of the plaque was drastically decreased when platelets lacked EP3. In conclusion, PGE2 facilitates the initiation of arterial thrombosis and, hence, contributes to atherothrombosis. Inhibition of the platelet EP3 receptor should improve prevention of atherothrombosis

Neutrophils recruited by leukotriene B4 induce features of plaque destabilization during endotoxaemia

Aims: Both leukotrienes and neutrophils have been linked to plaque destabilization. Despite being evoked, the role of leukotriene B4 (LTB4) in neutrophil recruitment to plaques and the concomitant effects of these two actors on plaque stability remain to be proven. Since both actors are elicited during endotoxaemia, a condition associated with the risk of cardiovascular events, we investigated whether endotoxaemia promotes LTB4-mediated neutrophil infiltration in plaques and explored the roles of LTB4 and neutrophils in plaque destabilization. Methods and results: Endotoxaemia induced by repeated peritoneal endotoxin injections at a non-lethal dose (1.5 mg/kg, 5 days) in chow-fed aged Apoe-/- mice (over 45 weeks old) resulted in neutrophil infiltration and activation in plaques. Subsequently to neutrophil invasion, plaques exhibited increased features of vulnerability: reduced collagen content, expanded necrotic cores, and thinned fibrous caps. These plaque features were reproduced by direct deposition of isolated neutrophils onto murine atheromatous carotid arteries in an in vivo assay. In endotoxemic mice, plaques produced increased amounts of LTB4. Genomic or pharmacological impairments of this production reduced neutrophil infiltration, collagenolysis, and apoptosis of smooth muscle cells in plaques of endotoxemic mice. Furthermore, conditioned media of human culprit plaques (CPs) contained more LTB4 than non-CPs and levels of LTB4 correlated to both neutrophil activation markers and endotoxin releases in CPs. Conclusion: These results show that the increased neutrophil recruitment elicited by LTB4 contributes to increase features of plaque destabilization in endotoxemic contexts and point out LTB4 as a potential therapeutic target in atherosclerosis

The kinesin Kif21b regulates radial migration of cortical projection neurons through a non-canonical function on actin cytoskeleton

International audienceCompletion of neuronal migration is critical for brain development. Kif21b is a plus-end-directed kinesin motor protein that promotes intracellular transport and controls microtubule dynamics in neurons. Here we report a physiological function of Kif21b during radial migration of projection neurons in the mouse developing cortex. In vivo analysis in mouse and live imaging on cultured slices demonstrate that Kif21b regulates the radial glia-guided locomotion of newborn neurons independently of its motility on microtubules. We show that Kif21b directly binds and regulates the actin cytoskeleton both in vitro and in vivo in migratory neurons. We establish that Kif21b-mediated regulation of actin cytoskeleton dynamics influences branching and nucleokinesis during neuronal locomotion. Altogether, our results reveal atypical roles of Kif21b on the actin cytoskeleton during migration of cortical projection neurons

A LYSA Phase Ib Study of tazemetostat (EPZ-6438) plus R-CHOP in newly diagnosed Diffuse Large B Cell Lymphoma (DLBCL) patients with poor prognosis features.

International audiencePurpose:The histone-methyl transferase EZH2, catalytic subunit of the PRC2 complex involved in transcriptional regulation, is mutated in approximately 25% of germinal center B-cell lymphomas. Aberrant proliferative dependency on EZH2 activity can be targeted by the orally available EZH2 inhibitor tazemetostat (EPZ-6438). We report the results of the phase Ib tazemetostat plus R-CHOP combination (NCT02889523), in patients 60 to 80 years of age with newly diagnosed diffuse large B-cell lymphoma.Patients and Methods:The primary objective of this dose-escalation study was to evaluate the safety of the combination and to determine the recommended phase II dose (RP2D) of tazemetostat.Results:A total of 17 patients were enrolled. During C1 and C2, two dose-limiting toxicities were observed: one grade 3 constipation at 400 mg and one grade 5 pulmonary infection at 800 mg. Grade 3 or more toxicities observed in more than 10% of the patients were constipation (24%), nausea (12%), and hypokalemia (12%). Grade 3 to 4 hematologic adverse events were recorded in 8 patients (47%): neutropenia (47%), leukopenia (29%), anemia (18%), and thrombocytopenia (12%). The tazemetostat RP2D was 800 mg. No organ-oriented toxicity increased with tazemetostat dosage escalation (severity and incidence). At 800 mg, AUC and Cmax of tazemetostat were similar compared with the single-agent study (E7438-G000-101).Conclusions:The RP2D of tazemetostat combined with R-CHOP is 800 mg twice a day. The association presents safety and PK comparable with R-CHOP alone. Preliminary efficacy data are encouraging and further investigations in phase II trial are warranted

Ciliogenesis and cell cycle alterations contribute to KIF2A-related malformations of cortical development.

Genetic findings reported by our group and others showed that de novo missense variants in the KIF2A gene underlie malformations of brain development called pachygyria and microcephaly. Though KIF2A is known as member of the Kinesin-13 family involved in the regulation of microtubule end dynamics through its ATP dependent MT-depolymerase activity, how KIF2A variants lead to brain malformations is still largely unknown. Using cellular and in utero electroporation approaches, we show here that KIF2A disease-causing variants disrupts projection neuron positioning and interneuron migration, as well as progenitors proliferation. Interestingly, further dissection of this latter process revealed that ciliogenesis regulation is also altered during progenitors cell cycle. Altogether, our data suggest that deregulation of the coupling between ciliogenesis and cell cycle might contribute to the pathogenesis of KIF2A-related brain malformations. They also raise the issue whether ciliogenesis defects are a hallmark of other brain malformations, such as those related to tubulins and MT-motor proteins variants

TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis

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MYC-IG rearrangements are negative predictors of survival in DLBCL patients treated with immunochemotherapy: a GELA/LYSA study.

Diffuse large B-cell lymphoma (DLBCL) with MYC rearrangement (MYC-R) carries an unfavorable outcome. We explored the prognostic value of the MYC translocation partner gene in a series of MYC-R de novo DLBCL patients enrolled in first-line prospective clinical trials (Groupe d'Etudes des Lymphomes de l'Adulte/Lymphoma Study Association) and treated with rituximab-anthracycline-based chemotherapy. A total of 774 DLBCL cases characterized for cell of origin by the Hans classifier were analyzed using fluorescence in situ hybridization with BCL2, BCL6, MYC, immunoglobulin (IG)K, and IGL break-apart and IGH/MYC, IGK/MYC, and IGL/MYC fusion probes. MYC-R was observed in 51/574 (8.9%) evaluable DLBCL cases. MYC-R cases were predominantly of the germinal center B-cell-like subtype 37/51 (74%) with no distinctive morphologic and phenotypic features. Nineteen cases were MYC single-hit and 32 cases were MYC double-hit (MYC plus BCL2 and/or BCL6) DLBCL. MYC translocation partner was an IG gene in 24 cases (MYC-IG) and a non-IG gene (MYC-non-IG) in 26 of 50 evaluable cases. Noteworthy, MYC-IG patients had shorter overall survival (OS) (P = .0002) compared with MYC-negative patients, whereas no survival difference was observed between MYC-non-IG and MYC-negative patients. In multivariate analyses, MYC-IG predicted poor progression-free survival (P = .0051) and OS (P = .0006) independently from the International Prognostic Index and the Hans classifier. In conclusion, we show in this prospective randomized trial that the adverse prognostic impact of MYC-R is correlated to the MYC-IG translocation partner gene in DLBCL patients treated with immunochemotherapy. These results may have an important impact on the clinical management of DLBCL patients with MYC-R who should be routinely characterized according to MYC partner gene. These trials are individually registered at www.clinicaltrials.gov as #NCT00144807, #NCT01087424, #NCT00169143, #NCT00144755, #NCT00140660, #NCT00140595, and #NCT00135499